Axial flow fans



3,006,417 AXIAL FLCW FANS Jan C. Busquet, Hengelo Netherlands, assignor to Koninklijke Machinefabriek Gebr. Stork 8L Co. NSV.,

Hengelo Netherlands Filed Dec. 15, 1953, Ser. No. 780,444 Claims priority, application Netherlands Jan. 15, 1953 2 Claims. (Cl. Mii-160.23)

This invention relates to an axial flow fan, having a hollow impeller hub and adjustable blades rotatably Supported with their shanks in the closed hollow hub body, said blade Shanks being connected to an adjusting rod extending into the hollow hub body and being coupled to a control mechanism for axially displacing said rod. When adjusting the impeller blades variations of pressure occur in the hub body, so that particularly along the blade Shanks air or gas will flow into and out of the hub body. Thereby particularly with a fan operating with air or gas containing dust the drawback occurs that dust penetrates into the impeller hub and reaches also the bearings of the blade Shanks. Said drawback also arises if for other reasons the pressure at the outside of the hub body is higher than that reigning in the interior of the hub body.

The invention has for its object to remove said drawback and to prevent dust penetrating into the impeller hub. According to the invention the impeller shaft or the adjusting rod is provided with a channel which on the one side communicates with the cavity of the hub body and on the other side is connected to a chamber located outside the impeller hub and communicating with a source of air or gas having a pressure exceeding that reigning at the outside of the impeller hub. With said arrangement the pressure in the cavity of the impeller hub will also exceed that at the outside of the hub, so that air or `gas may ow out of the impeller hub but no air or gas containing dust can penetrate from the outside into the hollow hub body.

The invention will further be described with reference to the accompanying drawing showing a sectional elevation of part of a fan according to the invention.

The impeller hub 1 is hollow and closed by a cover plate 2 secured to the circumferential wall 3 of the hub body. The impeller blades 4 with their Shanks 5 are supported in an intermediate rim 6 of the hub body. A lever 7 is secured to each inner end of the blade Shanks and pivotally connected to an adjusting disk 9 by means of a pin 8. Said adjusting disk is secured on a hollow rod 10, projecting out of the hub body and adapted to be axially displaced on the impeller shaft 11. The central part 13 of the cover plate 12 is sealed at 12 with respect to the hollew rod 10.

The displacement of the disk 9 for adjusting the blades 4 is obtained by an adjusting rod 14 secured to a Sleeve 15 connected to a sleeve 17 rotatably supported on the rod by a ball bearing 13 but prevented from axial displacement on said rod. Upon displacement of the sleeve 17 by means of adjusting rod 14 the hollow rod 10 with the adjusting disk 9 for adjusting the impeller blades will therefore also be displaced.

The chamber 19 formed in the sleeve 17 is sealed with respect to the thickened end 20 of the impeller shaft 11. Secured in the wall of Sleeve 17 is a tube 21 extending with its thickened end 22 in a stationary 3,05Al7 Patented Oct.. 31, 1961 pipe 23, in which air or gas may enter, which has a pressure exceeding that reigning at the outside of the impeller hub. As the chamber 19 in the sleeve 17 is in communication with the cavity in the impeller hub by means of a channel 24 in the shaft 11 there will also reign a higher pressure in the hub, so that no air or gas from the outside can penetrate into the hub.

Thereby the interior of the hub and also the bearings of the blade Shanks are kept free from dust.

The pipe 23 is adapted to supply air from the outside of the fan casing and the inlet of said pipe may be provided with a filter. The pipe 23 may also be connected to the pressure side of the fan and be provided with a lter. If desired the pipe 23 may also be connected to a source of air or gas under pressure.

What I claim is:

1. An axial ow fan comprising, in combination, a rotary main shaft, a closed hollow :hub mounted on Said shaft, adjustable impeller blades rotatably supported by and externally of the hub, said hub and said blades constituting together the impeller of the fan, Shanks associated with the blades and passed through the peripheral wall of the hub, a control mechanism mounted for axial movement on the Shaft and passed through a side wall of the hub in a gas tight manner, Said control mechasism being operatively connected with the Shanks of the blades, a casing forming part of the external portion of the control mechanism and detning a closed chamber, at least one passage interconnecting said chamber and the cavity ywithin the hollow hub, and a source of gas communicating with said chamber and having a pressure exceeding that reigning at the outside of the hub.

2. An axial ilow fan comprising, in combination, a rotary main shaft, a `closed hollow hub mounted on said Shaft, adjustable impeller blades rotatably supported by and externally of the hub, said hub and said blades constituting together the impeller of the fan, Shanks associated with the blades and passed through the peripheral wall of the hub, control means mounted for axial movement on the shaft passing through a side wall of the hub in a gas tight manner and operatively connected with the Shanks of the blades, said means including a Sleeve mounted for axial movement on the shaft and passed through said side wall of the hub in a gas tight manner, the end portion of said sleeve projecting into the hub being coupled with the Shanks of the blades, and a casing mounted vfor axial movement only with the shaft outside the impeller and defining a closed chamber, said sleeve and said casing forming parts of Said control mechanism and being interconnected for relative rotation and joint axial movement, at least one passage interconnecting said chamber and the interior of the hollow hub, and a source of gas communieating with said chamber and having a pressure exceeding that reigning at the outside of the hub.

References Cited in the le of this patent UNITED STATES PATENTS 2,390,068 Adams Dec. 4, 1945 FOREIGN PATENTS 930,674 Germany July 21, 1955 

